Storage apparatuses are equipped with a plurality of storage devices configured to store data, and a storage controller configured to control the storage devices, wherein the object thereof is to provide a data storage space having a large capacity to a host computer.
There storage apparatuses are required to save a large amount of data at a low cost. In order to satisfy such demands, a technique is known to record data via lossless compression (hereinafter simply referred to as compression). If data size is reduced by compression and recorded in the storage device, cost of retaining data (such as bit cost of storage medium or cost of power consumed by the storage apparatus) can be reduced.
If data is compressed and recorded in the storage device, overhead of compression processing occurs during write and overhead of decompression processing of compressed data occurs during read, such that the access performance may be deteriorated. In order to avoid this drawback, a technique related to selectively performing compression of data exits. For example, patent literature 1 discloses a storage system configured to manage a plurality of storage tiers, in which data moved to a lower tier is compressed and stored.